It is previously known catheters for postsurgical drainage of wound secretion, whereby the catheter tube in its one end, the rear one, is connected to a suction source providing a weak vacuo and with its front end is placed in a wound area, where secretion is formed postsurgically during healing. The catheter is hereby provided with a through-extending lumen and in its front end provided with laterally arranged openings, so called eyes, which are going through the tube wall and through which the secretion is removed by suction. The arrangement of such a secretion drainage has proved to improve healing considerably and thereby reduce the hospital care time, which is positive both to the patients and the society.
It has now, however, been shown that the present type of catheters, having a number of eyes in the side-walls, causes tissue to be sucked into the lumen, i.a. due to the close proximity of the catheter to the tissue, and expand into the lumen. This further causes, when the catheter is removed, that a very high force, relatively considered, has to be applied to draw the catheter free from the wound area, which causes the formation of a trauma in the wound. The traction power has thereby been measured to 3-4 kp.
In so called surgical aspirators, i.e. aspirators used for removing blood and wound secretion during a pending surgical incision and which aspirators work with high vacuo and high flow rates, it is known to arrange different types of devices to provide for simultaneous passage of air, whereby the suction force is reduced and provides for an atraumatic suction.
Such devices cannot, however, be used in postsurgical wound drainage, as the catheter then is completely embedded in the tissue to be drained and an excess of air is not present.
Further it is known from the prior art, FR No. 2,240,026 and FR No. 2,248,057, a catheter provided with longitudinally extending wide slots, which run either axially or helically and in which slots the eyes are arranged through the walls. These catheters, however, do not solve the problem of an atraumatic removal of the catheter as the tissue will be sucked into the eyes and the lumen to the same extent as if no slots were present.
Prior art, U.S. Pat. No. 3,590,820, further recognizes an aspirator tip comprising a number of longitudinally extending bores, which are connected with the outer surface via a slot, whereby each bore at the very front end of the tip is connected with an inner lumen of the tip by means of a perpendicular bore arranged thereto, i.e. a bore arranged radially from the outer surface of the tip to the inner lumen. The slots and bores are provided in order to obtain a suction of air when the tip is used to remove blood and secretion during a surgical incision, whereby the tip is connected to a high vacuo source. The aspirator tip is only intended for use at surgical incisions and not to be used in postsurgical drainage, where it, if so used, will not give an atraumatical removal due to the radially bores, or passages.
Depending upon the above-mentioned drawbacks, demands have been raised for a catheter for said use which eliminates the suction-in of tissue into the lumen and which makes it possible to considerably reduce, and at least halve the traction power needed at the removal of the catheter, whereby the risk for trauma would be considerably reduced.